1. Field of the Invention
The present invention relates to a variable capacity wobble plate type compressor used, not exclusively but preferably, for air-conditioning a car compartment, and more particularly, to a variable capacity wobble plate type compressor provided with a pressure-responsive piston drive mechanism including a variable angle non-rotary wobble plate, and a capacity regulating valve for regulating a compressor capacity by controlling a pressure level in a crankcase in which the piston drive mechanism is received.
2. Description of the Related Art
U.S. Pat. No. 4,730,986 to Kayukawa et al discloses a variable capacity wobble plate type compressor having a wobble angle control valve controlling the compressor capacity in response to a change in a cooling load. The wobble angle control valve comprises two valves; one for controlling a supply of a high pressure gas into a crankcase in which a pressure-sensitive piston drive mechanism is received, and the other for controlling the evacuation of a blowby gas from the crankcase. Namely, the variable displacement wobble plate type compressor of U.S. Pat. No. 4,730,986 is provided with a variable angle non-rotary wobble plate; a suction chamber for refrigerant before compression; a discharge chamber for refrigerant after compression; suction, compression and discharge cylinder bores; pistons reciprocated by the wobble plate within the cylinder bores for compressing the refrigerant; a crankcase with a crank chamber receiving therein a pressure-responsive piston drive mechanism including a wobble plate mounted about a drive shaft connectable to a rotary drive source; a first communication passageway permitting an adjustable supply of a high pressure gas from the discharge chamber into the crankcase chamber; a first control valve for closing and opening the first passageway in response to a change in a fluid pressure indicative of a refrigerating load change; a second communication passageway for permitting an adjustable evacuation of a blowby gas from the crankcase chamber to the suction chamber; and a second control valve changing an extent of an opening of the second communication passageway in response to an electrical signal or signals indicating a change in a physical value relative to the air-conditioning circuit and the vehicle, as well as in response to a change in a fluid pressure level in the crankcase chamber. Nevertheless, the above-mentioned first control valve does not include a means capable of adjustably changing a reference value, with respect to which a fluid pressure change causes an operation of the first control valve to adjustably open and close the first communicating passageway for supplying the high pressure gas, and therefore, the control operation of the first control valve is not satisfactory from the view point of the capability thereof to respond to an extremely large change in a cooling load of an air-conditioning circuit. The second control valve is able to assist the obtaining of an accurate operation of the first control valve, but is unable to broaden the capability of the response characteristic of the first control valve.
Japanese Unexamined (Kokai) Patent Publication No. 63-16177 discloses another variable capacity wobble plate type compressor having a capacity control valve. The compressor of the JP-A-63-16177 includes a crank chamber defined by a crankcase; a drive shaft extended in the crank chamber and rotatably supported by the crankcase; a rotary member fixedly mounted on the rotatable drive shaft; a rotary drive member mounted around the drive shaft and pivoted on the rotary member via a hinge mechanism, to change an angle of inclination with respect to the drive shaft; a wobble plate non-rotatably mounted on an inclining surface of the rotary drive plate and performing a wobbling motion in response to a rotation of the drive shaft; a plurality of pistons connected to the wobble plate to reciprocate in corresponding cylinder bores in response to the wobbling of the wobble plate; a suction chamber for receiving a refrigerant gas to be supplied to the cylinder bores; a discharge chamber into which the refrigerant gas after compression is discharged from the cylinder bores; and a valve means arranged in a gas evacuation passageway extending between the crank chamber and the suction chamber--the valve means adjustably changing a pressure prevailing in the crank chamber to cause a change in the angle of inclination of the wobble plate, to thereby vary an amount of suction of the refrigerant gas into the cylinder bores. The above-mentioned valve means comprises a regulating valve capable of opening and closing the gas evacuation passageway, a pressure-responsive means connected to the regulating valve and controlling the operation of the regulating valve in response to a change in a pressure in the suction chamber, and an external control means connected to the pressure-responsive means and providing the pressure-responsive means with a load varying in response to an externally applied signal, to thereby adjustably change a reference pressure value of the pressure-responsive means. Namely, the reference pressure value of the pressure-responsive means can be freely changed by the external control means in such a manner that the pressure sensing characteristics of the pressure-responsive means are widely changed, and thus a large change in the operation characteristics of the regulating valve occurs. Accordingly, the above-mentioned valve means is able to adjust the pressure in the crank chamber at any level among a wide range of pressure levels, and therefore, the amount of stroke of the respective reciprocating pistons can be adjusted so that a desired compressor capacity-ranging from a very small to a very large capacity value, can be obtained. Consequently, it is possible to maintain a low evaporating temperature of the refrigerant gas and to reduce a cooling load applied to the compressor by lowering a capacity of the compressor.
Nevertheless, in the variable capacity wobble plate type compressor of the JP-A-63-16177, the valve means is arranged in the gas evacuation passageway communicating between the crank chamber and the suction chamber, and accordingly, a pressure rise in the crank chamber must be accomplished by a blowby gas leaking from the compression chambers in the cylinder bores during the compression stroke of the pistons. Accordingly, for example, when a car is to be rapidly accelerated, a pressure level in the crank chamber of the compressor must be quickly raised to rapidly change the operation of the compressor from a large to a smaller capacity, to lower a load applied to the car engine. When the valve means is closed, however, since the speed of raising the pressure level in the crank chamber is necessarily low, the compressor cannot quickly vary the capacity thereof, and therefore, a lowering of the load applied to the car engine is not achieved.